A CONTINUOUSLY TUNABLE 2-5 MICRON LASER USING INTRACAVITY SHIFTING IN A DIODE LASER PUMPED Cr:LiSAF OSCILLATOR

A continuously tunable laser source covering the 2-5 micron wavelength region is proposed. Light generated by a diode laser pumped tunable Cr:LiSAF laser is Raman shifted twice in Hydrogen to nicely cover the 205 micron window. The unique feature of the proposed laser is that the Raman shifting cell and optics are placed inside the pump laser cavity. As a result sufficient gain and interaction length are obtained even at the lower powers available from diode pumping. The intercavity Raman cell uses two focusing mirrors to contain the first Stokes and partially contain the second Stokes beam. This approach benefits from the high intensities inside the laser cavity and by effectively increasing the Raman interaction lenth by the Q of the shifting cavity. If the cavity is properly designed the second Stokes beam will grow from four wave mixing. The work proposed here will investigate several of the issues related to phase matching of the four wave mixing process. The results will be combined with an optical design study for a prototype design to be fabricated in Phase II.